Generating an image of a seal impression

ABSTRACT

A method and apparatus for generating an image of a seal impression. Irradiation of a face of a seal with N beams of light striking the face in succession from N respective different directions respectively corresponding to N different angles of incidence of the light on the face is caused, the face having a character thereon, N≧2. N still images of the face corresponding respectively to the N beams are acquired, each still image structured as pixels including a RGB color combination. The N still images are combined to generate a composite image of pixels that includes a common area of pixels that commonly appears on the face of the seal in all still images, the common area having a luminance value exceeding a specified luminance threshold, the common area including a character area pertaining to where the engraved character is located on the face of the seal.

TECHNICAL FIELD

The present invention relates generally to an apparatus and method forgenerating an image of a seal impression, and more particularly to anapparatus and method for generating an image of a seal impression byphotographing the face of a seal.

BACKGROUND

It is a common practice to enter information on digital forms in orderto promote paperless procedures. A problem arises when a seal needs tobe affixed on a digital form. In such a case, typically a seal isaffixed on paper, then the seal is scanned with a scanner to acquire animage of the seal, and the image is put on the digital form. However,true paperless cannot be achieved by this method.

It has been conventionally known to pick a seal impression by directlytaking an image of a seal-impression face (the face of a seal) with a TVcamera. However, there is a problem that, when the face of a seal isordinarily photographed, it is not possible to discriminate between acharacter part and a carved part on the face of the seal with highaccuracy.

BRIEF SUMMARY

The present invention provides a method for generating an image of aseal impression, said method comprising:

causing, by a processor of an information processing apparatus,irradiation of a face of a seal with N beams of light striking the facein succession from N respective different directions respectivelycorresponding to N different angles of incidence of the light on theface, said face having a character engraved thereon, said N at least 2;

said processor acquiring N still images of the face correspondingrespectively to the N beams of light striking the face in succession,each still image structured as a set of pixels such that each pixelcomprises a red-green-blue (RGB) color combination; and

said processor combining the N still images to generate a compositeimage of pixels, said combining comprising generating in the compositeimage a common area of pixels that commonly appears on the face of theseal in all still images of the N still images, said common area havinga luminance value exceeding a specified luminance threshold, said commonarea including a character area pertaining to where the engravedcharacter is located on the face of the seal.

The present invention provides an information processing apparatus,comprising a processor, a memory coupled to the processor, and acomputer readable storage device coupled to the processor, said storagedevice containing program code configured to be executed by theprocessor via the memory to implement a method for generating an imageof a seal impression, said method comprising:

said processor causing irradiation of a face of a seal with N beams oflight striking the face in succession from N respective differentdirections respectively corresponding to N different angles of incidenceof the light on the face, said face having a character engraved thereon,said N at least 2;

said processor acquiring N still images of the face correspondingrespectively to the N beams of light striking the face in succession,each still image structured as a set of pixels such that each pixelcomprises a red-green-blue (RGB) color combination; and

said processor combining the N still images to generate a compositeimage of pixels, said combining comprising generating in the compositeimage a common area of pixels that commonly appears on the face of theseal in all still images of the N still images, said common area havinga luminance value exceeding a specified luminance threshold, said commonarea including a character area pertaining to where the engravedcharacter is located on the face of the seal.

The present invention provides a computer program product, comprising acomputer readable storage device having a computer readable program codestored therein, said program code configured to be executed by aprocessor of an information processing apparatus to implement a methodfor generating an image of a seal impression, said method comprising:

said processor causing irradiation of a face of a seal with N beams oflight striking the face in succession from N respective differentdirections respectively corresponding to N different angles of incidenceof the light on the face, said face having a character engraved thereon,said N at least 2;

said processor acquiring N still images of the face correspondingrespectively to the N beams of light striking the face in succession,each still image structured as a set of pixels such that each pixelcomprises a red-green-blue (RGB) color combination; and

said processor combining the N still images to generate a compositeimage of pixels, said combining comprising generating in the compositeimage a common area of pixels that commonly appears on the face of theseal in all still images of the N still images, said common area havinga luminance value exceeding a specified luminance threshold, said commonarea including a character area pertaining to where the engravedcharacter is located on the face of the seal.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram generally illustrating an exemplary configuration ofa seal impression image generation system, in accordance withembodiments of the present invention.

FIG. 2 is a diagram illustrating an exemplary configuration of a sealimpression capturing apparatus, in accordance with embodiments of thepresent invention.

FIG. 3 is a diagram illustrating an exemplary configuration of the sealimpression capturing apparatus, in accordance with embodiments of thepresent invention.

FIGS. 4( a) and 4(b) depict a diagram for explaining an incident angleof light from a Light Emitting Diode (LED) in accordance withembodiments of the present invention.

FIGS. 5( a), 5(b), and 5(c) are diagrams for explaining areas that arebright because of diffuse reflection of light, in accordance withembodiments of the present invention.

FIG. 6 is a diagram for explaining the relationship between thepositions of bright areas and light irradiation directions, inaccordance with embodiments of the present invention.

FIG. 7 is a diagram for explaining a method for combining three stillimages, in accordance with embodiments of the present invention.

FIG. 8 is a block diagram illustrating an exemplary functionalconfiguration of an information processing apparatus, in accordance withembodiments of the present invention.

FIG. 9 is a flowchart illustrating an exemplary operation of theinformation processing apparatus, in accordance with embodiments of thepresent invention.

DETAILED DESCRIPTION

The present invention will be described below in detail with referenceto the accompanying drawings.

The present invention generates an image of a seal impression by takingan images of the face of a seal, improve the accuracy of the generatedimage of the seal impression.

The present invention provides an apparatus generating an image of aseal impression by taking an image of the face of a seal, the apparatusincluding: a light irradiation section capable of irradiating the faceof the seal with light from N directions (N: an integer of 2 or more) atsuch an angle that a shadow with a length of the radius of the face ofthe seal or longer is formed; an image-taking section taking an image ofthe face of the seal; an acquisition section acquiring N taken images bycontrolling the light irradiation section so as to irradiate the face ofthe seal with light from one direction among the N directions andcontrolling the image-taking section so as to take an image of the faceof the seal which is irradiated with the light from the one direction bythe light irradiation section, the acquisition section performing thecontrols for each of the N directions; and a generation sectiongenerating an image of the seal impression by extracting a part havingbrightness equal to or above a criterion in all of the N taken imagesacquired by the acquisition section.

Here, the light irradiation section may include N light-emitting devicesand the acquisition section may control the light irradiation section soas to turn on one of the N light-emitting devices to irradiate the faceof the seal with light from the one direction. Alternatively, the lightirradiation section may include one light-emitting device and theacquisition section may position the light-emitting device in one of Npositions relative to the face of the seal to control the lightirradiation section so as to irradiate the face of the seal with lightfrom the one direction.

In the apparatus, the angle formed by any two adjacent virtualdirections among N virtual directions which are images projected on avirtual plane including the face of the seal in the N directions may be(360° /N)°.

Furthermore, N in the apparatus may be 3.

The present invention also provides an apparatus for generating an imageof a seal impression by taking an image of the face of a seal, theapparatus including: a first light-emitting device provided at aposition capable of irradiating the face of the seal with light at suchan angle that a shadow with a length equal to or longer than the radiusof the face of the seal is formed, from a first direction correspondingto a first virtual direction, an image being projected onto a virtualplane including the face of the seal in the first direction; a secondlight-emitting device provided at a position capable of irradiating theface of the seal with light at such an angle that a shadow with a lengthequal to or longer than the radius of the face of the seal is formed,from a second direction corresponding to a second virtual direction at120° to the first virtual direction, an image being projected onto thevirtual plane in the second direction; a third light-emitting deviceprovided at a position capable of irradiating the face of the seal withlight at such an angle that a shadow with a length equal to or longerthan the radius of the face of the seal is formed, from a thirddirection corresponding to a third virtual direction at 120° to thefirst virtual direction and different from the second virtual direction,an image being projected onto the virtual plane in the third direction;a camera provided at a position capable of taking an image of the faceof the seal; an acquisition section acquiring a first taken image bycausing the camera to take an image of the face of the seal which isirradiated with light from the first direction by causing the firstlight-emitting device to light up, acquiring a second taken image bycausing the camera to take an image of the face of the seal which isirradiated with light from the second direction by causing the secondlight-emitting device to light up, and acquiring a third taken image bycausing the camera to take an image of the face of the seal which isirradiated with light from the third direction by causing the thirdlight-emitting device to light up; and a generation section generatingan image of the seal impression by extracting a part having brightnessequal to or above a criterion in all of the first taken image, thesecond image and the third image acquired by the acquisition section.

The present invention further provides a method for generating an imageof a seal impression by taking an image of the face of a seal, themethod including: a light irradiation step of irradiating the face ofthe seal with light from one direction among N directions (N: an integerof 2 or more) at such an angle that a shadow with a length of the radiusof the face of the seal or longer is formed; an image-taking step oftaking an image of the face of the seal which is irradiated with lightfrom the one direction at the light irradiation step; an acquisitionstep of acquiring N taken images by performing the light irradiationstep and the image-taking step for each of the N directions; and ageneration step of generating an image of the seal impression byextracting a part having brightness equal to or above a criterion in allof the N taken images acquired by the acquisition step.

The present invention further provides a computer program (i.e.,software, program code, etc.) stored on a storage device, said computerprogram causing a computer to function as an apparatus for generating animage of a seal impression by taking an image of the face of a seal, theprogram causing the computer to function as: an acquisition sectionacquiring N taken images (N: an integer of 2 or more) obtained byperforming a process of irradiating the face of the seal with light fromone direction among N directions at such an angle that a shadow with alength of the radius of the face of the seal or longer is formed and aprocess of taking an image of the face of the seal which is irradiatedwith light from the one direction, for each of the N directions; and ageneration section generating an image of the seal impression byextracting a part having brightness equal to or above a criterion in allof the N taken images acquired by the acquisition section.

Here, the program may further cause the computer to function as acontrol section that controls a light irradiation section so as toperform, for each of the N directions, a process of irradiating the faceof the seal with light from the one direction, the light irradiationsection being capable of irradiating the face of the seal with lightfrom the N directions, and an image-taking section taking image of theface of the seal so as to perform, for each of the N directions, aprocess of taking an image of the face of the seal irradiated with lightfrom the one direction by the light irradiation section.

The present invention can improve the accuracy of an image of a sealimpression generated by taking images of the face of a seal.

In one embodiment, a surface where a character is engraved (hereinafterreferred to as the “seal face”) is irradiated with light at an acuteangle so that shadows of the rim and the character are formed and stillimages of the seal face are taken with a CCD (Charge Coupled Device)camera. Such shooting is performed while changing the direction of lightirradiation direction in increments of 120° C., and three still imagesare stored in a memory of an information processing apparatus. The threestill images stored are superimposed together, so that bright parts thatare common to the three still images can be extracted. Thus, an image ofthe seal impression that is very close to an image of a seal impressionaffixed on paper can be contactlessly extracted. This enables an imageof the seal impression to be superimposed on a digital form or the likeon the information processing apparatus. Thus, paperless management ofdocuments that require seal impressions can be achieved. Furthermore,the image of the seal impression can be registered so that an image of aseal impression affixed on a paper form can be checked against theregistered seal impression image.

A first way to change the light irradiation direction may be lit up, oneafter another, three light sources placed in such positions that thedirection of light irradiation changes in increments of 120°. A secondway is to position a single light source in thee positions, from oneposition to another, that are set relative to a seal so that theirradiation direction of light from the single light source changes inincrements of 120°. While the first way is used in this embodiment, thesecond way may be used.

FIG. 1 is a block diagram illustrating an exemplary configuration of aseal impression image generation system, in accordance with embodimentsof the present invention.

As illustrated, the seal impression image generation system includes aninformation processing apparatus 10 and a seal impression capturingapparatus 20 which are interconnected through a USB cable 30.

The information processing apparatus 10 includes a CPU (CentralProcessing Unit) 11, which is computational processing means, a memory12 and a hard disk 13, which are storage means, and a USB controller 14,which is a communication means. The CPU 11 executes various kinds ofsoftware such as an OS (Operating System) and applications to implementthe present invention, which will be described later in conjunction withFIG. 8. The memory 12 is a storage space for storing various kinds ofsoftware and data used for executing the various kinds of software toimplement methods of the present invention by the software beingexecuted by the CPU 11 via the memory 12. The hard disk 13 is a tangiblestorage device for storing data input in various kinds of software anddata output from the various kinds of software. The USB controller 14sends and receives information to and from the seal impression capturingapparatus 20 through the USB cable 30. Thus, the information processingapparatus 10 comprises a processor (e.g., CPU 11), a memory 12 coupledto the processor, and a computer readable storage device (e.g., harddisk 13) coupled to the processor. The storage device contains programcode (i.e., software) configured to be executed by the processor via thememory to implement the methods of the present invention. A computerprogram product of the present invention comprises a computer readabletangible storage device having computer readable program code (i.e.,software) stored therein, the program code (i.e, software) configured tobe executed by the processor to implement the methods of the presentinvention.

The seal impression capturing apparatus 20 includes a USB camera 21,LEDs (Light Emitting Diodes) 22 a, 22 b and 22 c, an USB LED controller23, and a USB HUB unit 24. The USB camera 21 is connected to theinformation processing apparatus 10 through the USB cable 30 andprovides taken images to the information processing apparatus 10 fordisplay. The USB camera 21 is one example of image-taking section. TheLEDs 22 a, 22 b and 22 c are light-emitting devices that emit light whencurrent flowing through them. The LEDs are hereinafter sometimescollectively referred to as the LED 22 unless distinction among them isnecessary. The USB LED controller 23 turns on and off switches on wiresconnected to the LEDs 22 a, 22 b and 22 c. The combination of the LEDs22 a, 22 b and 22 c and the USB LED controller 23 is one example of alight irradiation section. The USB HUB unit 24 forwards a signal forcontrolling shooting with the USB camera 21 to the USB camera 21 andforwards a signal for controlling turning on and off of the LEDs 22 a,22 b and 22 c to the USB LED controller 23.

In the seal impression image generation system described above, the USBcamera 21 connected to the information processing apparatus 10 isdisposed in a position facing the face of a seal in the seal impressioncapturing apparatus 20.

FIG. 2 is a cross-sectional view of the seal impression capturingapparatus 20, taken along a plane passing through the central axis ofthe seal and the LED 22 a, in accordance with embodiments of the presentinvention.

As illustrated, the seal impression capturing apparatus 20 includes acamera unit 211 and a lens 212 which make up the USB camera 21. The lens212 is disposed in such a way that the lens surface is parallel to theseal face 28 of a seal 27 to enable an image of the seal face to betaken from the direction perpendicular to the seal face 28.

While the seal impression capturing apparatus 20 includes the LEDs 22 a,22 b and 22 c, only the LED 22 a is depicted because the LEDs aredisposed in such positions that the irradiation directions of light areat an angle of 120° to one another and therefore only the LED 22 a is inthe plane of the cross section.

The seal impression capturing apparatus 20 further includes a lightshield 25 for preventing light from the LED 22 a from being directlyincident on the seal face 28. The light shield 25 has an opening in aposition coinciding with the lens 212 to allow the USB camera 21 to takea picture of the seal face 28.

The seal impression capturing apparatus 20 further includes a reflector26 a at an end of the light shield 25 with a slight gap between them.The reflector 26 a reflects light emitted from the LED 22 a toward theseal face 28. The gap between the light shield 25 and the reflector 26 aserves as a slit for allowing light from the LED 22 a to be linearlyincident on the seal face 28.

While the USB camera 21 is disposed above the seal 27, the position ofthe USB camera 21 is not limited to this. The USB camera 21 may bedisposed in any position where an image of the face of a seal can betaken.

While the configuration shown in a cross-sectional view of the sealimpressing capturing apparatus 20 taken along a plane passing throughthe center axis of the seal 27 and the LED 22 a has been described, thesame description also applies to the configuration in a cross-sectionalview of the seal impression capturing apparatus 20 taken along a planepassing through the central axis of the seal 27 and the LED 22 b, and across-sectional view of the seal impression capturing apparatus 20 takenalong a plane passing through the central axis of the seal 27 and theLED 22 c.

FIG. 3 is a diagram of the seal impression capturing apparatus 20 viewedfrom the seal side, in accordance with embodiments of the presentinvention. FIG. 3 illustrates an image of the seal impression capturingapparatus 20 projected on a virtual plane including the seal face 28,viewed from the seal side. Parts that are directly visible from the sealside are represented by solid lines and parts that are not visible fromthe seal side are represented by dashed lines.

As illustrated, the outer circumferences of the light shield 25, thecamera unit 211, and the lens 212 constitute concentric circles aboutthe center S of the seal face 28 of the seal 27. Note that the circlebetween the outer circumference of the light shield 25 and the outercircumference of the camera unit 211 represents the fold of the lightshield 25 and the circle inside the outer circumference of the lens 212represents the opening of the light shield 25.

The LEDs 22 a, 22 b and 22 c are disposed in such a manner that linesegments SA, SB, and SC are at an angle of 120° to one another, where A,B and C are the positions of the LEDs 22 a, 22 b and 22 c (the positionsof images of the LEDs 22 a, 22 b and 22 c projected on the virtual planeincluding the seal face 28), respectively, viewed from the seal side.

The reflectors 26 a, 26 b and 26 c are disposed in such a manner thatthe positions of the reflectors 26 a, 26 b and 26 c (the positions ofimages of the reflectors 26 a, 26 b and 26 c projected on the virtualplane including the seal face 28) viewed from the seal side are on aline extended from line segment SA on the A side, on a line extend fromline segment SB on the B side, and on a line extended from line segmentSC on the C side, respectively. The reflectors are hereinafter sometimescollectively referred to as the reflector 26 unless distinction amongthem is necessary.

An angle of irradiation of seal face 28 with light from the LED 22 willbe described below.

FIGS. 4( a) and 4(b) (collectively, “FIG. 4”) illustrate irradiation ofthe seal face with light from the LED 22 at an irradiation angle set sothat shadows of the rim of the seal and the character are formed, inaccordance with embodiments of the present invention. LEDs are used aslight sources because LEDs emit light that travels highly rectilinearly.The seal face 28 of the seal 27 is irradiated with light emitted fromthe LED 22 and traveling through a slit.

As illustrated, when the condition “θ≦arctan (h/R)” is satisfied, itfollows that L≧R, where θ is the angle of irradiation with LED 22, R isthe radius of the seal face, h is the depth of the engraved part of theseal face other than the character, and L is the length of shadows ofthe rim 272 and the character 274 on the seal face 28.

The radius R of the seal face 28 in this case is equal to the distancefrom the center of the seal face to the outer circumference of the rim272 of the seal 27 and therefore includes the width of the rim of theseal whereas the length L of the shadows is equal to the distance froman end of the shadows to the inner circumference of the rim of the sealand therefore does not includes the width of the rim of the seal. Itseems that the width of the rim of the seal affects the conditions givenabove. However, the width is not included in the condition because thewidth of the rim of the seal is undetermined in this embodiment. Thewider the rim, the farther the end of the shadow will be located fromthe direction of light irradiation. Accordingly, if the condition“θ≦arctan (h/R)” is satisfied, then the relation L≧R always holdsregardless of the width of the rim of the seal, and exclusion of thewidth of the rim of the seal does not cause a problem.

FIG. 4( a) depicts only the presence of the LED 22 in the direction oflight irradiation and does not depicts light from the LED 22 beingreflected by the reflector 26 before being incident on the seal face.That is, the LED 22 does not necessarily need to be disposed in such aposition that light is reflected by the reflector 26 before beingincident on the seal face. The LED 22 may be disposed in any positionwhere irradiation can be accomplished at an angle to form a shadowlonger than the radius of the seal face.

FIG. 4( b) illustrates shadows formed on the seal face 28 when the angleof irradiation 8 with the LED 22 satisfies the condition “θ≦arctan(h/R)”. The hatching in FIG. 4( b) represents the shadows. The shadowsare formed in areas that occupy more than a half of the engraved areaexcluding the character on the seal face and extend toward the directionopposite to the irradiation direction of the LED 22. Specifically, ashadow of the rim 272 of the seal is formed in an area 271 and a shadowof the character 274 is formed in an area 273. There are also areas inthe engraved area other than the character on the seal face, such as anarea 275, where no shadow is formed.

In practice, there are slightly brighter areas on the side irradiatedwith light diffusely reflected by curved parts on the rim 272 of theseal 27 and the edges of the character 274, and ink residuals in curvedshapes.

FIGS. 5( a), 5(b), and 5(c) (collectively, “FIG. 5”) are diagrams forexplaining slightly bright areas, in accordance with embodiments of thepresent invention.

FIG. 5( a) illustrates shadows formed on the seal face 28 of the seal 27when the angle of irradiation θ with the LED 22 satisfies the condition“θ≦arctan (h/R)” as in FIG. 4( b). The areas 271 to 275 are the same asthose in FIG. 4( b). FIG. 5( a) also depicts a slightly bright area 277at the rim 272 of the seal face and a slightly bright area 279 at theedge of the character 274.

FIG. 5( b) is an enlarged view of parts enclosed in the dashed boxes inFIG. 4( a).

An area on the rim 272 of the seal and an area (area X) on the surfaceof the character 274 are bright because the areas are directlyirradiated with light from the LED 22. Since the engraved area (area Z)other than the character 274 on the seal face is deeper by h, shadows ofthe rim 272 of the seal and the character 274 are formed to darken thearea Z. On the other hand, an area on the rim 272 of the seal and anarea on the edge of the character 274 on the LED 22 side (area Y) areslightly bright because there are curved parts and ink residuals whichform angles likely to cause diffuse reflection.

FIG. 5( c) is a cross-sectional view of the seal face corresponding to(b).

A protruding part 281 corresponds to area x in (b) whereas a recessedpart 282 corresponds to area Z in FIG. 5( b). The boundary part 283between the protruding part 281 and the recessed part 282 corresponds toarea Y in (b) where there are curved parts and ink residuals.

Still images are taken with the USB camera 21 under the conditionsdescribed above in one embodiment.

Here, the positions of the bright area 275 in the engraved area, otherthan the character in the seal face and the areas 277 and 279 (area Y inFIG. 5( b)), are bright because of diffusely reflected light thatdepends on the light irradiation direction.

FIG. 6 is a diagram for explaining the relationship between thepositions of bright areas and light irradiation directions, inaccordance with embodiments of the present invention. Hereinafter, theLED 22 a is denoted as LED0, indicating that the light irradiationdirection is 0°, the LED 22 b is denoted as LED120, indicating that thelight irradiation direction is 120°, and the LED 22 c is denoted asLED240, indicating that the light irradiation direction is 240°.

A still image PIC0 taken while irradiating with light from LED0 containsbright areas 277 and 279 at edges of the rim 272 of the seal 27 and thecharacter 274 in the direction of 0° as illustrated. The still imagePIC0 also contains a bright area 275 in the direction opposite to 0°where a shadow of the rim 272 is not formed.

A still image PIC120 taken while irradiating with light from LED120contains slightly bright areas 277 and 279 at edges the rim 272 of theseal 27 and the character 274 in the direction of 120°. The still imagePIC120 also contains a bright area 275 in the direction opposite to 120°where a shadow of the rim 272 of the seal is not formed.

A still image PIC240 taken while irradiating with light from LED240contains slightly bright areas 277 and 279 at edges of the rim 272 ofthe seal 27 and the character 274 in the direction of 240°. The stillimage PIC240 also contains a bright area 275 in the direction oppositeto 240° where a shadow of the rim 272 of the seal is not formed.

The bright parts common to the three still images are the surface of theseal face 28 excluding engraved parts, curved parts and parts wherethere are ink residuals. The bright parts are equivalent to a sealimpression that would be left on paper after the seal was put on thepaper. Therefore, the three still images are combined in thisembodiment.

FIG. 7 is a diagram for explaining a method for combining the stillimages, in accordance with embodiments of the present invention.

In this embodiment, image processing is performed to logically AND threestill images PIC0, PIC120, and PIC240 to form the composite image PIC asillustrated. Specifically, the bright areas 272 and 274 (see FIG. 5(a)), that is, the areas that have brightness equal to or higher than acriterion, common to all of the three still images PIC0, PIC120 andPIE240 are extracted and inserted into the composite image PIC. As aresult, areas that depend on the direction of irradiation with light areeliminated from the still images, so that only the sufficiently brightareas 272 and 274 of the seal face are on the composite image PIC,forming an image of a seal impression. The seal impression image isstored as an image against which a seal impression can be checked.

A configuration and operation of the information processing apparatus 10of the seal impression image generation system described above will bedescribed below.

FIG. 8 is a block diagram illustrating an exemplary functionalconfiguration of the information processing apparatus 10, in accordancewith embodiments of the present invention.

As illustrated, the information processing apparatus 10 includes an LEDcontrol section 51 and an image acquisition section 52. The informationprocessing apparatus 10 also includes a superimposition section 53, abinarization section 54, a light-dark reversal section 55, a colorconversion section 56, and an unwanted part removal section 57.

The LED control section 51 turns on and off switches on lines connectedto LED0, LED120 and LED240 to control the LEDs so as to light up oneafter another. In this embodiment, the LED control section 51 isprovided as one example of a control section that controls a lightirradiation section so as to perform a process for sequentiallyirradiating a seal face with light from N directions, one directionafter another. Thus, the LED control section 51 causes irradiation of aface 28 of a seal 27 with N beams of light, from N LEDs, striking theface in succession from N respective different directions respectivelycorresponding to N different angles of incidence of the light on theface, which is represented by steps 501, 503, and 505 (see FIG. 9) in anembodiment in which N=3. The face of the seal has a character engravedthereon. Generally, N at is least 2.

The image acquisition section 52 controls the USB camera 21 so as totake an image of the seal impression every time the LED0, LED120 orLED240 is lit to acquire still images PIC0, PIC120 and PIC240. It shouldbe noted that a still image actually taken with the USB camera 21 is amirror image of an image of a seal impression on paper. Therefore, it isassumed here that the still images PIC0, PIC120 and PIC240 are imagesobtained by mirroring, by a setting in the image acquisition section 52or the USB camera 21, images actually taken with the USB camera 21. Inthis embodiment, the image acquisition section 52 is provided as anexample of a control section that controls the image-taking section soas to perform a process of taking an image of a seal face irradiatedwith light from one direction for N directions and as an example of anacquisition section that acquires taken images. Thus, the imageacquisition section 52 facilitates acquiring N still images of the face28 corresponding respectively to the N beams of light striking the facein succession, which is represented by steps 502, 504, and 506 (see FIG.9) in an embodiment in which N=3. Each still image is structured as aset of pixels such that each pixel comprises a red-green-blue (RGB)color combination.

The superimposition section 53 superimposes the still images PIC0,PIC120 and PIC 240 acquired by the image acquisition section 52 on oneanother to generate a composite image. Specifically, the superimpositionsection 53 performs a process of rendering bright parts common to thestill images as bright parts in a composite image PIC and rendering darkparts in any of the still images PIC0, PIC120 and PIC 240 as dark partsin the composite image. The process may involve, for example, addingluminance values of each of R, G and B in the still images PIC0, PIC120and PIC240 pixel by pixel and normalizing the resulting values, bymultiplying the resulting values by a constant so that the largest valueof each of R, G and B after the addition becomes equal to the largestvalue of each of R, G and B before the addition. R, G, and B denote red,green, and blue, respectively. In this embodiment, the superimpositionsection 53 is provided as an example of a generation section thatextracts parts having brightness equal to or higher than a criterion togenerate an image of a seal impression.

The binarization section 54 binarizes the composite image generated bythe superimposition section 53. The binarization may be accomplished byrendering pixels having luminance levels (i.e., luminance values) higherthan a threshold as bright pixels having a luminance value of “1” andpixels having luminance values equal to or lower than the threshold asdark pixels having a luminance value of “0”, for example.

Thus, the superimposition section 53 and the binarization section 54collectively combine the N still images to generate a composite image ofpixels, which is represented by steps 507 and 508 (see FIG. 9) in anembodiment in which N=3. The combining of the N still images comprisesgenerating in the composite image a common area of pixels that commonlyappears on the face 28 of the seal 27 in all still images of the N stillimages. The common area has a luminance value exceeding a specifiedluminance threshold. The common area includes a character area 274pertaining to where the engraved character is located on the face of theseal. The common area may also include an outer rim 272 of the face.

In one embodiment, the combining of the N still images comprises: (i)adding the R, G, and B luminance values of corresponding pixels in the Nstill images to form the pixels of the composite image; (ii) normalizingthe pixels in the composite image such that the largest luminance valueof each of R, G and B in the composite image becomes equal to thelargest luminance value of each of R, G and B in the N still images; and(iii) rendering the pixels in the composite image having a luminancevalue exceeding and not exceeding the specified luminance threshold ashaving a luminance value of 1 and 0, respectively.

In one embodiment, the combining of the N still images comprises: (i)prior to the combining of the N still images, rendering the pixels ineach still image having a luminance value exceeding and not exceedingthe specified luminance threshold as having a luminance value of 1 and0, respectively; and (ii) logically ANDing the corresponding pixels inthe N still images to form the composite image.

Since the parts corresponding to the rim of the seal face and thecharacter are light and the engraved parts of the seal face are dark inthe composite image binarized by the binarization section 54, thelight-dark reversal section 55 reverses light and dark in the compositeimage. For example, the light-dark reversal section 55 renders pixelswith a luminance value of “1” to pixels with a luminance value of “0”and vice versa. Thus, the light-dark reversal section 55 implements:after the combining of the N still images, light and dark portions inthe composite image are reversed by (i) replacing the luminance valuesof 1 with luminance values of 0 and (ii) replacing the luminance valuesof 0 with luminance values of 1, which is represented by step 509 (seeFIG. 9).

Since the rim of the seal face and the character are represented inblack in the composite image light-dark-reversed by the light-darkreversal section 55, the color conversion section 56 performs a colorconversion process of converting black to red in one embodiment, whichis the color of seal ink, so that the image appears suitable as a sealimpression image. Thus in this embodiment, all pixels having a luminancevalue of 1 are converted to a color of sch as red, which is representedby step 510 (see FIG. 9).

The unwanted part removal section 57 removes unwanted parts of thecomposite image color-converted by the color conversion section 56 togenerate a seal impression image against which a seal impression can bechecked, which is represented by step 511 (see FIG. 9).

FIG. 9 is a flowchart of an example operation of the informationprocessing apparatus 10, in accordance with embodiments of the presentinvention.

As illustrated, first the LED control section 51 in the informationprocessing apparatus 10 turns on LED0 (step 501). With LED0 being on,the image acquisition section 52 causes the USB camera 21 to take animage of the face 28 of a seal 27 to acquire a still image PIC0 (step502). Note that after the still image PIC0 has been acquired, LED0 isturned off by the LED control section 51.

Then, the LED control section 51 turns on LED120 (step 503). With LED120being on, the image acquisition section 52 causes the USB camera 21 totake an image of the seal face 28 to acquire a still image PIC120 (step504). Note that after the still image PIC 120 has been acquired, LED120is turned off by the LED control section 51.

Then, the LED control section 51 turns on LED240 (step 505). With LED240being on, the image acquisition section 52 causes the USB camera 21 totake an image of the seal face 28 to acquire a still image PIC240 (step506). Note that after the still image PIC240 has been acquired, LED240is turned off by the LED control section 51.

Then the superimposition section 53 superimposes the still image PIC0acquired at step 502, the still image PIC120 acquired at step 504, andthe still image PIC240 acquired at step 506 together to generate acomposite image (step 507).

Then the binarization section 54 binarizes the composite image (step508).

The light-dark reversal section 55 then reverses light and dark in thebinarized composite image (step 509).

Then the color conversion section 56 performs a conversion process ofconverting black in the light-dark reversed composite image to red, forexample (step 510).

Finally, the unwanted part removal section 57 removes unwanted partsfrom the color-converted composite image (step 511).

While still images PIC0, PIC120 and PIC240 are superimposed to generatea composite image and then the composite image is binarized in thisexample of operation, the order of operations is not limited to this;light pixels and dark pixels in each of still images PIC0, PIC120 andPIC240 may be first rendered to “1” and “0”, respectively, to generate abinarized image, then the binarized images may be ANDed (logicalconjunction). The rendering of pixels is implemented in this embodimentby having luminance values higher than a threshold as bright pixelshaving a luminance value of “1” and pixels having luminance values equalto or lower than the threshold as dark pixels having a luminance valueof “0”.

In this way, an image of the seal face is taken while irradiating theseal face with light from each of the three directions, 0°, 120° and240° at such an angle that shadows with a length equal to the radius ofthe seal face or longer are formed. Then bright areas common to thethree still images taken are extracted from the images to generate animage of a seal impression, namely the composite image PIC in FIG. 7.Thus, a highly accurate image of the seal impression can be generated.

Furthermore, an image of the seal impression generated according to thisembodiment can be affixed to a digital form to display the highlyaccurate image of the seal impression on a screen of the imageprocessing apparatus 10. Once the owner of the seal has checked thedigital form and then attached his/her digital signature to lock theform, the digital form can be used as an authenticated document.

Moreover, the seal impression image generation apparatus according tothis embodiment allows one to digitize a seal impression with highaccuracy and readily affix the digitized seal impression on a digitalform at a window.

While the seal face is irradiated with light from three directions, 0°,120° and 240°, in this embodiment, the number of directions is notlimited to three. More generally, the face of a seal may be irradiatedwith N directions (where N is an integer greater than or equal to 2).

The angles formed by pairs of adjacent directions among the N directions(i.e., the angles formed by pairs of adjacent virtual directions among Nvirtual directions which are images projected on a virtual planeincluding the face of a seal in the N directions) may be the same orsome of the angles may be different. If all the angles are the same, theangles will be (360°/N)°. For example, if N=3, the angles will be 120°,as described above. Some of the angles are different for example if theface of the seal is irradiated with three directions, 0°, 120° and 270°,when N=3.

While still images taken by the seal impression capturing apparatus 20are sent to the information processing apparatus 10 through the USBcable 30 and image processing is applied to the still images in theinformation processing apparatus 10 to generate a seal impression imagein this embodiment, the present invention is not limited to this. Forexample, the seal impression capturing apparatus 20 may apply imageprocessing to still images taken by the seal impression capturingapparatus 20 to generate a seal impression image.

The descriptions of the various embodiments of the present inventionhave been presented for purposes of illustration, but are not intendedto be exhaustive or limited to the embodiments disclosed. Manymodifications and variations will be apparent to those of ordinary skillin the art without departing from the scope and spirit of the describedembodiments. The terminology used herein was chosen to best explain theprinciples of the embodiments, the practical application or technicalimprovement over technologies found in the marketplace, or to enableothers or ordinary skill in the art to understand the embodimentsdisclosed herein.

What is claimed is:
 1. A method for generating an image of a sealimpression, said method comprising: said processor causing irradiationof a face of a seal with N beams of light striking the face insuccession from N respective different directions respectivelycorresponding to N different angles of incidence of the light on theface, said face having a character engraved thereon, said N at least 2;said processor acquiring N still images of the face correspondingrespectively to the N beams of light striking the face in succession,each still image structured as a set of pixels such that each pixelcomprises a red-green-blue (RGB) color combination; and said processorcombining the N still images to generate a composite image of pixels,said combining comprising generating in the composite image a commonarea of pixels that commonly appears on the face of the seal in allstill images of the N still images, said common area having a luminancevalue exceeding a specified luminance threshold, said common areaincluding a character area pertaining to where the engraved character islocated on the face of the seal.
 2. The method of claim 1, wherein theface of the seal is circular and characterized by a radius, and whereineach beam forms on the face a shadow whose length is at least the radiusof the face.
 3. The method of claim 1, wherein said combining comprises:adding the R, G, and B luminance values of corresponding pixels in the Nstill images to form the pixels of the composite image; normalizing thepixels in the composite image such that the largest luminance value ofeach of R, G and B in the composite image becomes equal to the largestluminance value of each of R, G and B in the N still images; andrendering the pixels in the composite image having a luminance valueexceeding and not exceeding the specified luminance threshold as havinga luminance value of 1 and 0, respectively.
 4. The method of claim 1,wherein said combining comprises: prior to said combining, rendering thepixels in each still image having a luminance value exceeding and notexceeding the specified luminance threshold as having a luminance valueof 1 and 0, respectively; and logically ANDing the corresponding pixelsin the N still images to form the composite image.
 5. The method ofclaim 1, said method further comprising; after said combining, saidprocessor reversing light and dark portions in the composite image by(i) replacing the luminance values of 1 with luminance values of 0 and(ii) replacing the luminance values of 0 with luminance values of 1; andsaid processor converting all pixels having a luminance value of 1 to acolor of red.
 6. The method of claim 1, wherein the common area furtherincludes an outer rim of the face.
 7. The method of claim 1, wherein Nis at least
 3. 8. An information processing apparatus, comprising aprocessor, a memory coupled to the processor, and a computer readablestorage device coupled to the processor, said storage device containingprogram code configured to be executed by the processor via the memoryto implement a method for generating an image of a seal impression, saidmethod comprising: said processor causing irradiation of a face of aseal with N beams of light striking the face in succession from Nrespective different directions respectively corresponding to Ndifferent angles of incidence of the light on the face, said face havinga character engraved thereon, said N at least 2; said processoracquiring N still images of the face corresponding respectively to the Nbeams of light striking the face in succession, each still imagestructured as a set of pixels such that each pixel comprises ared-green-blue (RGB) color combination; and said processor combining theN still images to generate a composite image of pixels, said combiningcomprising generating in the composite image a common area of pixelsthat commonly appears on the face of the seal in all still images of theN still images, said common area having a luminance value exceeding aspecified luminance threshold, said common area including a characterarea pertaining to where the engraved character is located on the faceof the seal.
 9. The apparatus of claim 8, wherein the face of the sealis circular and characterized by a radius, and wherein each beam formson the face a shadow whose length is at least the radius of the face.10. The apparatus of claim 8, wherein said combining comprises: addingthe R, G, and B luminance values of corresponding pixels in the N stillimages to form the pixels of the composite image; normalizing the pixelsin the composite image such that the largest luminance value of each ofR, G and B in the composite image becomes equal to the largest luminancevalue of each of R, G and B in the N still images; and rendering thepixels in the composite image having a luminance value exceeding and notexceeding the specified luminance threshold as having a luminance valueof 1 and 0, respectively.
 11. The apparatus of claim 8, wherein saidcombining comprises: prior to said combining, rendering the pixels ineach still image having a luminance value exceeding and not exceedingthe specified luminance threshold as having a luminance value of 1 and0, respectively; and logically ANDing the corresponding pixels in the Nstill images to form the composite image.
 12. The apparatus of claim 8,said method further comprising; after said combining, said processorreversing light and dark portions in the composite image by (i)replacing the luminance values of 1 with luminance values of 0 and (ii)replacing the luminance values of 0 with luminance values of 1; and saidprocessor converting all pixels having a luminance value of 1 to a colorof red.
 13. The apparatus of claim 8, wherein the common area furtherincludes an outer rim of the face.
 14. The apparatus of claim 8, whereinN is at least
 3. 15. A computer program product, comprising a computerreadable storage device having a computer readable program code storedtherein, said program code configured to be executed by a processor ofan information processing apparatus to implement a method for generatingan image of a seal impression, said method comprising: causing, by aprocessor of an information processing apparatus, irradiation of a faceof a seal with N beams of light striking the face in succession from Nrespective different directions respectively corresponding to Ndifferent angles of incidence of the light on the face, said face havinga character engraved thereon, said N at least 2; said processoracquiring N still images of the face corresponding respectively to the Nbeams of light striking the face in succession, each still imagestructured as a set of pixels such that each pixel comprises ared-green-blue (RGB) color combination; and said processor combining theN still images to generate a composite image of pixels, said combiningcomprising generating in the composite image a common area of pixelsthat commonly appears on the face of the seal in all still images of theN still images, said common area having a luminance value exceeding aspecified luminance threshold, said common area including a characterarea pertaining to where the engraved character is located on the faceof the seal.
 16. The computer product of claim 15, wherein the face ofthe seal is circular and characterized by a radius, and wherein eachbeam forms on the face a shadow whose length is at least the radius ofthe face.
 17. The computer product of claim 15, wherein said combiningcomprises: adding the R, G, and B luminance values of correspondingpixels in the N still images to form the pixels of the composite image;normalizing the pixels in the composite image such that the largestluminance value of each of R, G and B in the composite image becomesequal to the largest luminance value of each of R, G and B in the Nstill images; and rendering the pixels in the composite image having aluminance value exceeding and not exceeding the specified luminancethreshold as having a luminance value of 1 and 0, respectively.
 18. Thecomputer product of claim 15, wherein said combining comprises: prior tosaid combining, rendering the pixels in each still image having aluminance value exceeding and not exceeding the specified luminancethreshold as having a luminance value of 1 and 0, respectively; andlogically ANDing the corresponding pixels in the N still images to formthe composite image.
 19. The computer product of claim 15, said methodfurther comprising; after said combining, said processor reversing lightand dark portions in the composite image by (i) replacing the luminancevalues of 1 with luminance values of 0 and (ii) replacing the luminancevalues of 0 with luminance values of 1; and said processor convertingall pixels having a luminance value of 1 to a color of red.
 20. Thecomputer product of claim 15, wherein the common area further includesan outer rim of the face.